Conversion of aliphatic hydrocarbons to cyclic hydrocarbons



Patented Aug. 20, 1940 CONVERSION OF ALIPHATIC HYDROCAR- BONS TO CYCLIC HYDROCARBONS Justus Friederich lands, assignor' pany, San Francisco, Delaware Clausen, Amsterdam, Netherto Shell Development Com- Calif.,' a corporation of N Drawing. Application November 26, 1938,

Serial No. 242,568. In the Netherlands December 17, 1937 9 Claims;

This invention relates to the treatment of hydrocarbons, and it more particularly relates to the production of cyclic hydrocarbons by the treatment of saturated and/or unsaturated aliphatic hydrocarbons or mixtures comprising one or a plurality of such aliphatic hydrocarbons.

An object of the invention is to provide a practical and economical process for the catalytic treatment of hydrocarbon mixtures, such as mineral oil compositions, containing one or more saturated and/or unsaturated aliphatic hydro-- carbons whereby at least a part of the aliphatic hydrocarbon content of the treated mixture is converted to naphthenic and/or aromatic type hydrocarbons to result in a more valuable product of higher cyclic hydrocarbon content.

Another object of the invention is to provide a practical and economical process for the conversion of normal or only moderately branched chain aliphatic hydrocarbons of parafilnic or olefinic character, which preferably contain at least six carbon atoms in the aliphatic chain, to aromatic hydrocarbons and/or naphthenic hydrocarbons.

The process of the invention comprises contacting the individual hydrocarbons of aliphatic, character or a mixture comprising one or more of such hydrocarbons at an elevated temperature, preferably in the range of from about 400 C. to 600 C., with a solid catalyst mass consisting of or essentially comprising a heavy metal salt of molybdic acid or tungstic acid.

I have found that the heavy metal salts of molybdic and tungstic acids, and mixtures essentially comprising one or a plurality of such heavy metal salts, are particularly suitable agents for effecting the conversion of hydrocarbons of aliphatic character to cyclic hydrocarbons, and can be used, with the attainment of commercially practicable yields of cyclic hydrocarbons at temperatures below those at which excessive cracking of the treated and resultant hydrocarbon material occurs. Moreover, it has been found that catalysts consisting of or comprising a heavy metal salt of molybdic or tungstic acid, particularly when the process is effected in the initial presence of added hydrogen'under a moderately elevated pressure, retain their activity over relatively long periods of continuous use and can. when they have finally suffered loss of activity. to the extent that their use is no longer practicable, be reactivated and their initial activity substantially restored easily and inexpensi ely.

While broadly applicable to the conversion of hydrocarbons of aliphatic character to cyclic hydrocarbons, the invention is of particular value and usefulness as applied to the conversion to cyclic hydrocarbons of the aliphatic hydrocarbons of paraflinic or olefinic character which are of straight or-only slightly branched structure and possess at least six carbon atoms in the aliphatic chain. Individual aliphatic hydrocarbons of this preferred subgroup are, among others, normal hexane, the normal hexylenes, 2- methyl pentane, the Z-methyl pentylenes, normal heptane, the normal heptylenes, Z-methyl heptane, the Z-methyl heptylenes, B-methyl hep tane, the E-methyl heptylenes, the normal and only slightly branched octanes, the normal and only slightly branched octylenes, the normal and only slightly branched nonanes and nonylenes and the like. The paraffinic or olefinic normal or only slightly branched carbon skeleton hydrocarbons may be advantageously treated individually, in admixture with each other, or in admixture with one or more other hydrocarbons not of the particular preferred group such as the butanes, the butylenes, the pentanes, the amylenes; the naphthenes, the cyclic olefi'nes, and the. like.

The process of the invention may be advantageously applied to the treatment of hydrocarbon mixtures such as the natural gasolines, for example, the straight-run gasolines, hydrogenation gasolines, gasolines obtained by cracking, gasolines obtained by polymerization of olefines. followed by hydrogenation of the polymers, gasolines obtained by the reaction of carbon monoxide and hydrogen, and the like. Such hydrocarbon fuel mixtures, after treatment in accordance with the process of the invention whereby at least a part of their content of hydrocarbons of aliphatic character is converted to 40 cyclic hydrocarbons, have considerably higher octane numbers than the treated mixtures and are superior for motor fuel purposes. The resultant mixtures are also useful materials for blending with gasolines having lower octane numbers to improve said gasolines by raising their octane number.

The catalyst used in the execution of the invention consists of or comprises a heavy metal salt of an acid of the group consisting of tungstic acid and molybclic acid. Suitable catalysts are, for example, the tungstates and molybdates of the heavy metals such'as nickel, iron, cobalt, chromium, copper, manganese, vanadium, titanium, zirconium and the like.

and synthetic 30 The catalysts or catalyst compositions used in the execution of the process may be prepared in a variety of suitable manners known to the art. They may be used, alone or in admixture with one or more catalytic or contact materials, in any suitable solid form as powder, granules, pellets, pellules, etc., or they may together with other catalytic materials be supported on some suitable inactive or active carrying or supporting material such as charcoal, pumice, kieselguhr, fullers earth, silica gel, alumina, and the like. In some cases, it may be desirable to add tothe catalyst a small quantity of a substance capable of acting as a promoter.

The desired quantity of the catalyst, preferably in the form of pellules or granules, or supported on granules of a suitable carrier, is employed in manners customary in catalytic processes of this type. into a reaction tube or chamber made of any suitable material and of the desired capacity and heated to and maintained at the desired temperature while the hydrocarbon material to be treated is passed into contactwith it, preferably in the vapor phase, at the desired space velocity and under the desired pressure of operation.

The invention is preferably executed at a temperature in the range of from about 400 C. to 600 0., although higher or lower temperatures may in some cases be used advantageously. At temperatures below about 400 C., the catalyst is usually not sufficiently active to yield practical conversions. At temperatures greater than about 600 C., it may be difficult to obtain practicable conversions while avoiding excessive cracking and unduly rapid loss of activity of the catalyst. In general, the most favorable temperature in the preferred range of from 400 C. to 600 C., is dependent upon the particular hydrocarbon or hydrocarbon mixture treated, upon the particular catalyst or catalyst composition used, upon the contact time to be employed, and upon the desired pressure of operation.

The process of the invention may be executed at atmospheric, subatmospheric or superatmospheric pressure. It is preferably effected under moderately superatmospheric pressures of initially added hydrogen.- Such hydrogen pressures aid in maintaining the activity of the catalysts over relatively long periods of time while having substantially no deleterious effects on the extent of conversion to cyclic hydrocarbons of the treated material. The advantageous effects of the added hydrogen are best realized by operating under pressures of at least 10 atmospheres, a suitable pressure in some cases being about 50 atmospheres, and a suitable pressure range being from about 10 to about 100 atmospheres.

When the individual aliphatic hydrocarbons are cyclized, the reaction may or may not be effected in the presence of added hydrogen or in the presence of some diluent material. Suitable diluents, among which is nitrogen, are materials which have substantially no detrimental effect on the desired reaction and the catalyst under the conditions of execution of the process.

The optimum contact time to be employed will depend upon several factors such as the temperature of operation, the pressure of operation, the nature of the hydrocarbon or hydrocarbon mixture treated, the particular catalyst or catalyst composition used, the desired conversion per pass, etc. In general, when operating at temperatures of from 400 C. to 600 C. under hydrogen pressures of from about 10 to 100' atmospheres, good The catalyst may be packed ature of about 515 results are obtainable by employing contact times in the practical operating range of from about 10 to about 60 seconds. Shorter or longer contact times may be employed when necessary or desirable.

After the catalyst has, due to its use in the execution of the process, suffered loss of activity to the extent that its continued use is no longer practicable, it may be reactivated and its original activity partially or substantially completely restored by discontinuing the operation and passing air or some other suitable oxygen-containing or oxidizing gas into contact with the heated catalytic material. The reactivation may be effected in the presence of an added active or diluent gaseous material such as steam, carbon dioxide, nitrogen, etc. During the reactivation, the catalyst mass may be maintained at a temperature in the range of from about 300 C. to about 800 C. After a reactivation treatment with air, it may,'i.n some cases, be desirable to treat the heated reactivated catalyst with hydrogen prior to its reuse in the process.

The following examples are presented for the purpose of illustrating the invention as applied to the treatment of representative aliphatic hydro- Example I The hydrocarbon mixture treated was an octylene fraction which was fractionated from the product resulting from the vapor phase cracking of a solid paraffin wax. The octylene fraction boiled in the temperature range of about 113 C. to 137 0., had an octane number (C. F. R. motor method) of 51, and an octylene content (consisting principally of straight and only slightly branched chain octylenes) of about 85%.

The catalyst used was chromium tungstate, which material, in the form of particles of more or less uniform size, was packed into a reaction tube and heated to and maintained at a temper- C. while the gaseous octylene fraction, together with hydrogen, was passed into contact with it at such a rate that the average contact time was about 24 seconds, the pressure in the reaction tube being about 10 atmospheres.

The effluent reaction mixture was condensed and analyzed. A reaction product having an octane value of 70 was obtained in a yield of about 72% by weight; it contained about 15% by weight of aromatic hydrocarbons and about 30% by weight of naphthenes, the remainder consisting of a mixture of parafiin and olefine hydrocarbons.

Example II The hydrocarbon material treated was an octylene fraction similar to that described in Example I and consisting for the most part of straight or only slightly branched chain aliphatic hydrocarbons.

The catalyst was nickel tungstate, and it was used in a manner similar to that described in Example I. The catalyst was maintained at a temperature of about 540 C. while the octylene fraction, together with suificient hydrogen to make the operating pressure about 50 atmospheres, was passed into contact with it at such a rate that the average contact time was about 40 seconds.

The liquid reaction product obtained was found to contain about 29% by weight of aromatic hydrocarbons and about 31% by weight of naphthenic hydrocarbons, the remainder consisting of paraflins and olefines.

Results similar to those described may be obtained by the use of other catalysts of the class consisting of theheavy metal salts of molybdic and tungstic acid, other representative members oi the class being chromium molybdate, nickel molybdate, iron tungstate, iron molybdate, cobalt tungstate, cobalt molybdate, copper molybdate, etc. Analogous results are likewise obtainable by treatment of other aliphatic hydrocarbon mixtures as well as the individual aliphatic hydrocarbons.

While I have described my invention in a detailed manner and illustrated suitable modes of executing the same, it is to be understood that modifications may be made and that no limitations other than those imposed by the scope of the state catalyst at a temperature of from 400 C. to

600 C., said temperature being below that at which excessive cracking occurs.

2. A process for the conversion of an octylene to a cyclic hydrocarbon which comprises contacting an octylene with a preformed chromium tungstate catalyst at a temperature of from 400 C. to 600 C., said temperature being below that at which excessive cracking occurs.

3. A process for increasing the cyclic hydrocarbon content of a hydrocarbon mixture boiling essentially within the gasoline boiling range and containing a substantial amount of aliphatic hydrocarbons of at least six carbon atoms which comprises contacting the hydrocarbon mixture with a preformed heavy metal salt of an acid of the class consisting of the molybdic and tungstic acids at a temperature in the range of from 400 C. to 600 C., said temperature being below that at which excessive cracking occurs.

4. A process for the production of cyclic hydrocarbons which comprises contacting a. hydrocarbon mixture boiling essentially within the gasoline boiling range and containing in substantial amount at least one hydrocarbon of aliphatic character which contains at least six carbon atoms to the molecule with a preformed heavy metal salt of an acid of the class-consisting of molybdic and tungstic acids at a temperature in the range of from 400 C. to 600 C. and in the initial presence of added hydrogen under a pressure of at least 10 atmospheres, said temperature and partial pressure of hydrogen being below those at which excessive cracking occurs.

- 5. A process for the production of cyclic hydrocarbons which comprises contacting the vapors of, an aliphatic hydrocarbon boiling essentially within the gasoline boiling range and containing at least six carbon atoms with a preformed heavy metal salt of an acid of the class consisting of molybdic and. tungstic acids at a temperature of from 400 C. to 600 C. under a hydrogen pressure of from about 10 to about 100 atmospheres, said temperature and partial pressure of hydrogen being below those at which excessive cracking occurs. a

7. A process for the production of cyclic hydrocarbons which comprises contacting an aliphatic hydrocarbon boiling essentially within the.

gasoline boiling range and containing at least six carbon atoms, together with added hydrogen, with a catalyst essentially comprising a preformed heavy metal salt of an acid of the class consisting of molybdic and tungstic acids at a temperature of from 400 C. to 600C. and under a superatmospheric pressure, said temperature and partial pressure of hydrogen being below those at which excessive cracking occurs.

8. A process for the production of cyclic hydrocarbons which comprises contacting an aliphatic hydrocarbon boiling essentially within the gasoline boiling range and containing at least six gasoline boiling range and containing at least sixcarbon atoms with a catalyst essentially comprising a preformed compound of the group consisting of the nickelgiron, cobalt; chromium, copper, manganese, vanadium, titanium and zirconium molybdates and tungstates, at an elevated temperature equal to at least 400 C. but below the temperature at which excessive cracking of the hydrocarbon material occurs.

JUS'I'US FRIEDERICH CLAUSEN. 

